-
ane
~
u
-
comes down from the troposphere mainiy with rain; ac a comcequence
of accretion in chouds by the rapid uifxucive movemer.ts of the
tiny particles cauving them to hit the cloua droplets.
Ly the
same tyne of mecnaiiicm, contact with any cuxsface such au grass,
leaves, trees, etc., also wil. cauce deposition.
‘is a resuit of
tnic the mean reridence time 20 su.face air up to about
lJ,JUJ feet is avout three days ana the average residence time
for the whole tropocphece is about one montn.
The residence time
for the hisher part, the top 2J,JjJJ to 35,JJ0 feet, would be
cometning Like <5 day. with an expected steady state concentra~
tion perhaps ten to
£ fifteen
Now let us turn to the
cteatospuere.
times che value at the curface.
question of the cesidence time in the
This i: a very aifficuit one in the absence
:
ce
of reliatle data on the actua: quantity of »vomvy debris in the
St-atosphere.
Ii. che absence of firm direct measuremenitz, one
makes estimates of the stratospne.ic content by adding the
amount of radioactivity wnich i. tuiectea, subtracting the fal.out and subtractin, for the decay anc thu. calculating the
difference.
Ina cnii way numbers are derived which can be used
to compare with che inadequate info:mation tnat is available on
otratosphevic concert.
Mow it r2n't aiways cxeac just what
fraction of a boms falle out Llocaiiy and what fraction goes into
the stratosshere and troposphere.
lUowever, certain empivical
rues have been uced to estimace tsece rumbere.
These ave:
r
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